Method of making waterproof sheets or boards



Patented Feb. 13, 1940 UNIT-E METHOD OF MAKING WATERPROOF SHEETS OB BOARDS Harold L. Levin, Nutley, N. 1., assig'nor, by mesne assignments, to The Patent and Licensing Corporation, New York, N. Y., a corporation of Massachusetts No Drawing. Applicationlanuary 30, 1931, Serial No. 512,497

2 Claims. (CI. 92-21) This invention relates to improvements in the vention may be considered as applicable to the art of making waterproof sheets or boards, paruse of asphalts ranging in hardness from zero ticularly sheets or boards having waterproof and penetration (at 77 F. standard method of test) thermo-plastic properties to render the product and melting point of 200 F., to those having a suitable for use in the fabrication of automobile penetration of about 15 and a melting point uppanel board, flooring, box board, roofing elewards of 135 F. to approximately 200 F. ments, shoe elements, gaskets, binder board, in- In carrying out my invention in one of its terior or exterior facing or veneer panels, adverembodiments, an ordinary paper mill beater may tising signs, artistic or ornamental plaques or the be charged with a suitable quantity of fibrous Ike. An object of the invention is to provide an pulp and while the latter is being circulated improved process for efiectively combining a therein, the desired quantity of an asphalt of the Waterproof end/0r ermo-plastic substance with character above set forth, in the form of small fibrous pulp for the production of a stock that lumps or chunks, may be slowly fed to the beater, can e e fu y run on a p p making m while the contents thereof are maintained at norchine for the formation of homogeneous fibrous mal atmospheric temperatures, say 77 F., but

sheets or boards carrying substantial quantities preferably not in excess of 100 F. At the beof the waterproof and thermo-plastic binder uniginning of the operation it may be necessary to fcrmly distributed therethrcllghraise the beater roll. to some substantial distance More Spec fically a Object of t e nvention is above the bed plate in order to avoid undue me- 10 t provide a p ss of sp s r disintegratchanical strain that may be imposed by contact irlg normally friable, -p e, bitumineus with the lumps or chunks of relatively hard asor i m n-pi h type s n es in h pr s n e phalt circulating in the beater. As the action f wet p which acts as e p p i s n to a of the beater is continued or prolonged the lumps sufiiciently fine degree of subdivision or dispersion or h k of asphalt i gradually become 35 as to render the Particles capable f being duced to smaller fragments, as a result of the 35 sorbed on the surface of the fibres contained in ti d impact. cti n, and the beater roll the pulp. may then be gradually lowered closer towards the I have found i c da ce W e present bed plate so that on continued action the size invention that a binder of the character indiof th asphalt particles will be progressi l cated may be conditioned as aforesaid by a cond, Th operation is thus carri d on until tinned m i l mp as for e p under the asphalt is reduced to partcles of very small the action of the beate o of a di P p size which for the purposes of my invention m l e in the Presence Of Wet P p Circulatshould approximate an average particle size of mg in t e beaterabout mu. This serves to bring about a con- 5 T pr ss f y v ti is p d p dition in which the particles of. the asphalt have 35 larly for the utilization of bituminous substances developed sufficient surface energy so that they of a more or less hard friable character, such as are capable f being adsorbed on the surface p fi y phalts having pe etra and meltof the fibres contained in the stock and carry point relationships Within a range in which minute electric charges giving them capacity for 10 y lend themselves to grinding at normal ion adsorption and ability to respond to the acw mesp temperatures o a state in Which the tion of fiocculating electrolytes. I consider this particles (10 not coalesce but n storage unde o to be a rather important or significant feature in ipi n sin so as to h e to h other of my invention, as it insures the attainment of su c y so that some light mechanical numerous advantages of the invention as herein 15 placement is required to restore the individualized t forth d ,1 serves as guide i t llin a cond tion; but in which range they are susceptithe operation. In this latter respect it may be ble to fusion and coa escence a temperatures here pointed out that as the asphalt becomes disccmpereble to those usually pr v i n on the .integrated under the action of the beater into steam heated driers of a paper making machine. fragments of small size the color of the stock,

50 The bituminous substances espec ally contemas for example the grayish color that typifies news 50 plated for use in accordance with my invention, stock, will gradually change to the color of the generally speaking, have a steep susceptibility asphalt, the gradation in the color becoming more curve; that is to say they are susceptible to apparent as more asphalt'is put in and as the noticeable changes in penetration with slight asphalt becomes more finely div'ded, until when changes in temperature. Accordingly, my inthe particles have been reduced to a size approximating that indicated, only substantially small proportions of the asphalt particles will be discernible by the eye as discrete particles separate from the fibre and the stock takes on a homo-- geneous condition uniformly of the color of the asphalt. This condition will therefore serve as a guide to the operator as indicating the sumciency of the subdivision of the asphalt and ensures a condition which contributes greatly to the operation without gumming the instrumentalities of the paper machine, wet or dry end, and ensures uniform coating of. the fibres when the product has been coalesced in the drying action.

The quantity of asphalt that may thus be combined advantageously with fibrous pulp may vary up to several times the weight of the fibre in the stock and the exact quantity employed may accordingly be governed largely by the degree of waterproofness and/or thermo-plasticity desired in the product.

An important advantage of the operation thus described resides in the fact that it avoids the necessity for employing special equipment for conditioning the asphalt since the entire operation may beefiectively carried on in an ordinary paper mill beater.

, In respect to the advantages accruing from the process of my invention, according to which the asphalt may, and preferably is, caused to be subdivided into particles approximating the size hereinabove specified, I have found as above stated, that the particles in this state of subdivision acquire electrostatic charges, and are susceptible to adsorption of ions and/or protective colloids, and hence upon the addition of suitable flocculating electrolytes the pH of the system may readily be brought to the isoelectric point so as -to cause the particles of asphalt to cluster, clot or deposit upon the fibres.

One of the advantages of this type of reduction resides in the fact that reduction in the presence of water only, does not result in particles of the desired average degree of fineness within a reasonable time and further, when reduced with water the particles do not wet readily with water, and tend to float on the water medium.

Illustrating the application of my invention to various types of fibrous stock and various bituminous substances falling within the range to which the invention is particularly applicable, I may cite as an example the use of an asphalt known in the trade as B-grade California, having a penetration of 4 at 77 F. and a melting point of 175 F. which'may be worked up in the manner hereinabove described with a fibre furnish consisting substantially entirely of news, in the proportion of approximately equal parts of dry fibre and asphalt. A selected grade of coal tar pitch corresponding in properties approximately to the B-grade California asphalt may similarly be employed.

Another example of ingredients that may. be employed in carrying out the invention, particularly for the production of a light colored sheet or board is illustrated by the use of an asphalt known in the trade as Albino asphalt which is an asphalt characterized by a low asphaltene content and derived from a Borneo'crude, and having a penetration of approximately 12 and a melting point of approximately .135 'I' his may be worked up with an equal part by weight of a fibre furnish consisting approximately ?of equal parts of news and kraft. Inasmuch as asphalt of this type is normally of relatively light color, suitable proportions say 10 to 20% of pigment may be incorporated in the stock where a colored product is desired. Thus the furnish may be asi'ollows:

, Percent Albino asphal Red oxide pigment l5 Fibre 50 operation, the operation may be conducted by conditioning the bituminous material in the presence of part of the fibre furnish, in order to avoid I undue shortening of the fibres and excessive hydration of the entire fibre furnish. After all of the asphalt has been dispersed the remainder of the fibre furnish may be added. Thus, for example, 300 parts by weight of an asphalt of 10 I penetration and a melting point of 145 F. may be treated in the beater as above described with parts by weight of kraft fibre circulating in the heater and after all the asphalt has been dispersed to the condition above described, 100 to 500 parts by weight more of kraft fibre may be added to the beater and the operation of the beater continued until the freshly added fibre has been uniformly disseminated through the stock. In those cases where the asphalt is of a softer or less friable variety falling within the range herein specified, it may be desirable in certain instances to introduce finely divided mineral mat- .ter into the asphalt in molten condition in order to render the asphalt more readily susceptible to disintegration by the operation of my process into particles of a size approximating 35 mu. For this purpose clay, diatomaceous earth, fuller's earth, slate dust, bentonite or similar substances may be employed in quantities ranging from 20 to 50% by weight of the asphalt. Where a material such as bentonite is employed for/this purpose the swelling action of the bentonite upon coming into contact with water will serve to facilitate the reduction of the asphalt to finely divided particles and in this case, as also in the case of other substances that may be employed for the purpose of rendering the asphalt more friable and susceptible to ready disintegration, the mineral matter may become adsorbed on the surface of the asphalt particles when they are reduced to the finely divided size herein contemplated, and thus serve further to stabilize the stock.

I have hereinabove referred to the ability of the asphalt particles when reduced to an average size approximating 35 mu to adsorb ions and protective colloids. Hence, where it is desired to provide additional peptization protection in the stock, substances such as bentonite, clay, animal or vegetable glue may be added to the stock in proportions of say 2 to 10% based on the dry weight. For this purpose also there may be used certain types of sulphonic acids preferably those of high molecular weight characterized by complete solubility in water and also solubility in solutions of calcium chloride. These sulphonic acids may be obtained from the acid tars resulting from the latter stages of a multi-stage sulphonation treatment of mineral oil fractions particularly lubricating oil. They may also be ob tained from the acid tars resulting from the sulphonation of non-aromatic hydrocarbons insoluble in liquid sulphur dioxide.

Where it is deemed necessary or desirable to ensure complete deposition or clustering of the asphalt particles upon the fibres contained in 1 the stock, suitable quantities of alum or similar substances may be added, preferably, in quantities which will be suflicient to bring the pH of the stock to the isoelectric point of the colloidal system.

While I have heretofore specified that the selected asphalt may be added in the form of lumps or chunks to the fibrous pulp circulating in the beater, it may be desirable in some instances to feed the same asphalt to the beater in a molten or heat liquefied condition thus facilitating the conveyance of the asphalt from the source of supply to the beater. It is to be understood therefore that the invention contemplates as an alternative method of introducing the asphalt into the beater, the feeding of the asphalt in molten condition. By maintaining the contents of the beater cold, substantially the same character of stock may be produced with the given asphalt, as where the asphalt is added to the beater in solid lumps or chunks, with all the attendant advantages thereof. In operating the process with this alternative mode of feeding the asphalt to the beater, the asphalt being at a temperature above the boiling point of water, and the contents of the beater being preferably not in excess of 77 F., the expansive forces of the steam generated when the hot asphalt impinges upon the aqueous fibrous suspension circulating in the beater will cause local foaming of the contents thus facilitating the reduction of the asphalt into particles of the desired size.

When the stock containing the desired types and relative quantities of fibre and binder has been conditioned as above described, it may then be conducted in the usual way to and over the paper making machine for formation into sheets. Thus, the stock may be fed to one or more of the cylinders of a multi-cylinder machine for the production of a multi-ply sheet and the formation dried in the usual way, the temperature of the steam heated driers being sufilcient to cause the composition so formed.

asphalt to fuse and coalesce, with the result that a homogeneous and uniform sheet is obtained in which the asphalt is contained in substantially continuous films on the fibres. Where boards of high caliper are desired the treated stock may be formed on the cylinder of a wet machine and the formation transferred by the usual blankets to the makeup roll, from which it may be stripped when the desired caliper has been built up, and dried and calendered in the usual way, thereby effecting fusion and coalescence of the asphalt particles distributed therethrough on the fibres, as already described.

The various stocks prepared as above described may also be formed on suction molds to form articles of hollow or irregular contour, such as fibre buckets, waste paper or other receptacles, toys, etc.

The expression friable as employed in the claims to qualify bituminous substances generally, or asphalt specifically, is intended to embrace such materials of this type, as fall within the range of hardness herein set forth and/or are susceptible to the treatments herein described.

I claim as my invention:

1. A process of producing a dispersion of thermoplastic binder substance which comprises mixing with said binder a quantity of. absorbent, finely divided non-fibrous matter under conditions to cause said binder to-be absorbed by said matter and form therewith a friable composition, and afterward dispersing in water the 2. A process of producing a pulp containing a binder substance, which comprises mixing a heat plastic binder with an absorbent, finely-divided inorganic matter to the extent of producing a friable mass, disintegrating said mass, and dispersing the disintegrated mass in a pulp of fibers in water suspension.

HAROLD L. LEVIN. 

